There is generally a limit on the diameter of a magnetic tape pack for video tape recorders. Therefore, in order to increase the amount of information that can be recorded, the magnetic tape is desirably made as thin as possible. However, if the tape is made thin, its mechanical strength becomes inadequate, and because of low "stiffness" or high stretchability the tape becomes susceptible to tape damage during running on video tape recorders.
The video tape is caused to run in contact with the fixed magnetic head, drum, guide poles, etc., so it is required to have low friction coefficient. Tapes having high friction coefficient cause large tension while they are running on the video tape recorder and are highly susceptible to tape damage. The term "tape damage" as used herein means the elongation and deformation of the magnetic tape, as well as the bending of the side edges of the tape that take place in recording or reproducing mode. The tape damage is caused during normal running but it is very likely to occur during loading or unloading. There are two types of video tape recorders, beta-type and VHS-type, and the occurrence of tape damage is more frequent in the VHS-type. The bending of the side edges of the tape easily occurs in a video tape recorder that uses loading posts having an acetal copolymer coating and which is a winding torque of about 300 g/cm or more during unloading. The bending occurs in the loading post assembly on the supply side as shown in FIG. 1 which is a schematic representation of a video tape recorder, and the direct cause of such bending is the rising or lowering of the tape at the loading post. The loading post is in contact with the surface opposite to the magnetic layer of the tape. The tape damage is a cause of skew, jitter and poor sound reproduction, and the tape bent at either side edge achieves very poor results in recording and reproducing modes.